The present invention relates to a system for and a method of monitoring at least one dynamic condition of a pneumatic tire, such as pressure.
The present invention relates to monitoring of conditions of a pneumatic tire, most importantly pneumatic pressure, and optionally temperature and/or tire revolution counting. Pressure (pneumatic pressure) is well known as a critical factor in pneumatic tire operation, most importantly if there is a loss of sufficient pressure to safely operate the tire, e.g., a xe2x80x9cflat tirexe2x80x9d. The (pneumatic) temperature is generally of secondary importance. Although it can be used to indicate an average temperature of the tire and wheel surrounding the pneumatic cavity, temperature is mostly used to normalize a pressure measured in a hot tire to a xe2x80x9ccold pressurexe2x80x9d value, i.e., the pressure as it would be in a xe2x80x9ccoldxe2x80x9d tire. When a pump system is included in order to regulate the air pressure in a tire, a pressure monitor can provide feedback to a vehicle operator about the status of the pressure regulation, which may very well be unable to regulate pressure under extreme conditions such as, for example, a large puncture or a blow-out of the tire. Revolution counting is often desired as an indication of tire usage. In general terms, as tire usage increases so does the risk of tire problem occurrence.
A great deal of prior art is devoted to apparatus and methods for measuring and monitoring rotary element and pneumatic conditions, particularly as they relate to pneumatic tire conditions.
For a century, the Goodyear Tire and Rubber Company of Akron Ohio, assignee of the present invention, has been the uncontested industry leader in tire product technology. For example, as early as 1892, a puncture-resistant tire was patented. In 1934, a year recognized as the beginning of the run-flat era, Goodyear introduced the Lifeguard (tm) safety tube, a fabric tube within the tire, used commercially by automakers and on trucks. In 1993, Goodyear""s Eagle GS-C EMT (Extended Mobility Technology) Tire won the Discover Award for Automotive Technological Innovation. In 1996, the Goodyear Eagle F1 run-flat tire was chosen as standard equipment on the 1997 Chevrolet C-5 Corvette.
Other examples of the strides Goodyear has taken in the advancement of tire and related technologies include, but are not limited to, the following patented inventions: Commonly-owned U.S. Pat. No. 3,665,387 (Enabnit; 1972), entitled SIGNALLING SYSTEM FOR LOW TIRE CONDITION ON A VEHICLE, incorporated in its entirety by reference herein, discloses a low tire pressure warning system adaptable for any number of wheels of a vehicle and providing dashboard indications of system operation and low pressure conditions while the vehicle is in motion.
Commonly-owned U.S. Pat. No. 3,831,161 (Enabnit; 1974), entitled FAIL-SAFE MONITORING APPARATUS, incorporated in its entirety by reference herein, discloses monitoring vehicle tire pressure wherein the operator is warned of an abnormal or unsafe condition of one or more of the tires.
Commonly-owned U.S. Pat. No. 4,052,696 (Enabnit; 1977), entitled TIRE CONDITION MONITOR, incorporated in its entirety by reference herein, discloses a tire condition sensing circuit that includes a ferrite element that changes from a ferromagnetic to a non-ferromagnetic state in response to a temperature increase above the material Curie point.
Commonly-owned U.S. Pat. No. 4,911,217 (Dunn, et. al.; 1990), entitled INTEGRATED CIRCUIT TRANSPONDER IN A PNEUMATIC TIRE FOR TIRE IDENTIFICATION, incorporated in its entirety by reference herein, discloses an RF transponder in a pneumatic tire. FIG. 1a of this patent illustrates a prior-art identification system (xe2x80x9creaderxe2x80x9d) that can be used to interrogate and power the transponder within the tire. The identification system includes a portable hand-held module having within it an exciter and associated circuitry for indicating to a user the numerical identification of the tire/transponder in response to an interrogation signal.
Commonly-owned U.S. Pat. No. 5,181,975 (Pollack, et. al.; 1993), entitled INTEGRATED CIRCUIT TRANSPONDER WITH COIL ANTENNA IN A PNEUMATIC TIRE FOR USE IN TIRE IDENTIFICATION, incorporated in its entirety by reference herein, discloses a pneumatic tire having an integrated circuit (IC) transponder and pressure transducer. As described in this patent, in a tire that has already been manufactured, the transponder may be attached to an inner surface of the tire by means of a tire patch or other similar material or device.
Commonly-owned U.S. Pat. No. 5,218,861 (Brown, et al.; 1993), entitled PNEUMATIC TIRE HAVING AN INTEGRATED CIRCUIT TRANSPONDER AND PRESSURE TRANSDUCER, incorporated in its entirety by reference herein, discloses a pneumatic tire having an integrated circuit (IC) transponder and pressure transducer mounted within the pneumatic tire. Upon interrogation (polling) by an external RF signal provided by a xe2x80x9creaderxe2x80x9d, the transponder transmits tire identification and tire pressure data in digitally-coded form. The transponder is xe2x80x9cpassivexe2x80x9d in that it is not self-powered, but rather obtains its operating power from the externally-provided RF signal.
The commonly-owned U.S. Patents referenced immediately hereinabove are indicative of the long-standing, far-reaching and ongoing efforts being made by the Goodyear Tire and Rubber Company in advancing tire product technology, particularly in the area of monitoring tire operating conditions.
Dynamic conditions such as revolution counting are readily determined. Straightforward tire revolution counters are well known, and are disclosed for example in U.S. Pat. Nos. 4,842,486 and 5,524,034, both of which are incorporated in their entirety by reference herein.
U.S. Pat. No. 5,218,862, incorporated in its entirety by reference herein, discloses a tire pressure monitor comprising wheel speed sensors located at the vehicle""s wheels to convey wheel speed information to an electronic controller. This patent notes that the wheel speed discrepancy between one tire to the others indicates the relative tire pressure, but that discrepancy may also be indicative of the vehicle turning, accelerating or decelerating, going up or down steep grades, or of one wheel slipping, or of a cross wind bearing on the vehicle.
U.S. Pat. No. 5,345,217, incorporated in its entirety by reference herein, discloses measuring wheel speed of a motor vehicle with a multi-tooth pulse generator on each wheel (as is used on electronic Anti-Lock Braking Systems) to produce a series of pulses spaced apart by equal increments of angular rotation of each wheel. The speed of each wheel is compared to the others, to determine if, and to what extent, a tire is deflated. U.S. Pat. No. 5,569,848, incorporated in its entirety by reference herein, discloses a system for monitoring tire pressure, comprising toothed ring sensors affixed to each wheel assembly, a sensor operatively associated with each respective toothed ring and producing signals that are a measure of the rotational velocity of the wheels, and a computer receiving signals from the sensors. The computer monitors the wheel speed sensors during vehicle operation, calculating and indicating vehicle speed, distance traveled by the vehicle and low tire pressure.
U.S. Pat. No. 3,588,814, incorporated in its entirety by reference herein, discloses an electric tire inflation indicator which determines the inflated condition of a tire by monitoring the rotational travel speed of the tire""s respective wheel, by means of a stationary reed switch and a magnet rotating with the wheel.
U.S. Pat. No. 5,749,984, incorporated in its entirety by reference herein, discloses a tire monitoring system and method utilizing a sensor in the tire to detect tire sidewall deflection and thereby determine tire pressure, tire speed and the number of tire revolutions.
In addition to the aforementioned dynamic conditions, static conditions are also associated with rotating elements such as pneumatic tiresxe2x80x94for example, pressure and temperature. Failure to correct quickly for improper tire pressure may result in excessive tire wear, blowouts, poor gasoline mileage and steering difficulties. An automatic tire deflation warning system is especially critical for xe2x80x9crun flatxe2x80x9d tires, where the deflated condition is barely detectable by the driver himself. Sensors for static parameters are typically located within the rotating tire, and associated circuitry can transmit data indicative of a sensed condition to an on-board receiver within the vehicle.
A xe2x80x9ctransponderxe2x80x9d is an electronic device capable of both receiving and transmitting radio frequency (RF) signals. Transponder systems, typically including a plurality of transponders and a single interrogator are well known and disclosed, for example, in U.S. Pat. No. 5,339,073, incorporated in its entirety by reference herein.
It is known to put transponders (and associated sensors) in pneumatic tires of motor vehicles. These transponders transmit a RF wave, with or without variable data (e.g., tire pressure, temperature, position) and/or fixed data (e.g., tire ID) to outside the tire, and receive RF signals, with or without data, from outside the tire. A separate transponder is typically associated with each tire of a motor vehicle to monitor and transmit tire-related data. Typically, an xe2x80x9cinterrogatorxe2x80x9d having both transmitting and receiving capabilities is used to communicate with the transponders. The interrogator may be xe2x80x9chand-heldxe2x80x9d, or mounted xe2x80x9con-boardxe2x80x9d the vehicle, or positioned along or in a roadway (e.g., xe2x80x9cdrive-overxe2x80x9d, or xe2x80x9cdrive byxe2x80x9d).
xe2x80x9cActivexe2x80x9d transponders have their own power supply (e.g., a battery). They transmit signals, and are typically also capable of receiving signals to control their functionality. xe2x80x9cPassivexe2x80x9d transponders are powered by the energy of an incoming RF signal, such as from an interrogator. Passive transponders fall into two general categories, those having only passive circuitry, and those having some active circuitry.
U.S. Pat. No. 5,612,671, incorporated in its entirety by reference herein, discloses a low tire pressure warning system having a pressure sensor and radio transmitter in each wheel, and a vehicle-mounted receiver including a microprocessor.
U.S. Pat. No. 4,609,905, incorporated in its entirety by reference herein, discloses a passive transponder having only passive circuitry. An RF transmitter in the vehicle interrogates the transponder, which reflects a predetermined harmonic of the RF signal back to a receiver as a function of the state of an associated pressure switch.
U.S. Pat. No. 4,067,235, incorporated in its entirety by reference herein, discloses a passive transponder with a tire pressure sensor. Electromagnetic radiation generated by a power transmitter is received by a receiving antenna comprising an inductor and a capacitor in the tire pressure sensor. This radiation is converted by a rectifier-filter to electricity to power active components (oscillator, buffer amplifier, transmitter) of the transponder.
U.S. Pat. No. 4,724,427, incorporated in its entirety by reference herein, discloses a passive transponder that receives a carrier signal from an interrogator. The carrier signal is rectified by a rectifying circuit connected across the transponder""s antenna coil to generate electricity to power the transponder. Data is encoded and mixed with the carrier signal in a balanced modulator circuit. The output of the balanced modulator circuit is transmitted back to the interrogator unit.
U.S. Pat. No. 4,703,650, incorporated in its entirety by reference herein, discloses a circuit suitable for one of many methods of coding for transmission the values of variables measured in a tire, and a device for monitoring tires employing such a circuit. An astable multivibrator transforms the measurement of the variable in question, for instance pressure and temperature, into a time measurement. The astable multivibrator delivers a pulse signal whose pulse width is a function of the temperature and the cyclic ratio of which is a function of the pressure. The signal is suitably transmitted from the tire to the vehicle by, for example, inductive coupling.
U.S. Pat. No. 4,730,188, incorporated in its entirety by reference herein, discloses a passive transponder excited by an inductive coupling from an interrogator. The transponder responds to the interrogator via the inductive coupling with a signal constituting a stream of data. The transponder comprises an induction coil serving as its antenna, and a full wave rectifier bridge and smoothing capacitor connected across the antenna to provide DC voltage (power) to active circuitry within the transponder.
U.S. Pat. No. 5,969,239, incorporated in its entirety by reference herein, discloses some forms of antennas for electromagnetically coupling moving transponders in tires to stationary antennas on the vehicle. The patent concerns replacing an annular coil type of rotating antenna with a smaller antenna integrated with the measurement sensor (transponder) in one small box firmly attached to the wheel, plus a closed circular strip-iron coupling ring attached to and coaxial with the wheel. The rotating antenna, stationary antenna and coupling ring are positioned so that electric current is induced in the coupling ring by magnetic flow in either of the antennas and vice versa. Alternate embodiments are mentioned which consider using the xe2x80x9cmetallic environmentxe2x80x9d in place of the ring of strip iron, for example the wheel itself, or at least one of the metallic beads of the tire. The frequency of transmission is from 30 to 100 kilohertz.
U.S. Pat. No. 5,824,891, incorporated in its entirety by reference herein, discloses xe2x80x9ca transmitting circuit . . . mounted on a frame member. The transmitting circuit includes a transmitting coil and generates electrical energy. . . . xe2x80x9d A xe2x80x9creceiving is inductively coupled to the transmitting circuit. The receiving circuit includes a sensor for generating a data corresponding to a physical characteristic of the vehicle wheel and a wireless communication circuit for receiving the electrical energy from the transmitting coil to remotely power the receiving circuit and for transferring the data signal from the receiving circuit to the transmitting circuitxe2x80x9d.
U.S. Pat. No. 4,911,217, incorporated in its entirety by reference herein, discloses an RF transponder in a pneumatic tire. FIG. 1a illustrates a prior-art identification system (xe2x80x9creaderxe2x80x9d) that can be used to interrogate and power the transponder within the tire. A portable hand-held module has within it an exciter and circuitry for indicating the numerical identification of the tire/transponder.
U.S. Pat. Nos. 5,181,975 and 5,218,861, incorporated in their entirety by reference herein, disclose a pneumatic tire having an integrated circuit passive transponder located within the structure of the tire for use in tire identification and pressure data transmission. The interrogation signal is rectified by circuitry in the transponder, which then utilizes the rectified signal as its source of electrical power for use in its transmission of digitally encoded signals.
U.S. Pat. No. 4,220,907, incorporated in its entirety by reference herein, discloses a low tire pressure alarm system for vehicles. Each wheel is provided with a transmitter, and there is a common receiver comprising a suitable antenna such as a ferrite loopstick.
U.S. Pat. No. 4,319,220, incorporated in its entirety by reference herein, discloses a system for monitoring tire pressure, comprising wheel units in the tires and a common receiver. Each wheel unit has an antenna comprising a continuous wire loop disposed against the inner periphery of the tire for transmitting signals and for receiving power. Multiple antennas may be provided for the receiver, and may be in the form of ferrite loopsticks.
U.S. Pat. No. 5,319,354, incorporated in its entirety by reference herein, discloses an antenna structure for communicating with an electronic tag (transponder) implanted in a pneumatic tire. This patent recognizes that the orientation of the transponder with respect to the antenna communicating with the transponder can adversely affect coupling between the interrogation antenna and the transponder antenna. A construction of an interrogation antenna is described so that, regardless of the position of the transponder in the pneumatic tire, a position of which is unknown, the coupling is always of the same quality.
International Publication No. WO 99/52722 (Oct. 21, 1999), incorporated in its entirety by reference herein, discloses a method and apparatus for sensing tire pressure in a vehicle wheel which is wireless. It employs xe2x80x9cknownxe2x80x9d pressure and temperature sensors, xe2x80x9cknownxe2x80x9d revolution detectors (e.g., ABS), and xe2x80x9cknownxe2x80x9d controllers. A transducer, the sensors, a power source (e.g., battery), and a transmitter are mounted on the wheel rim, interior to the tire. The transducer measures a pneumatic pressure and/or temperature and/or wheel speed that is converted into a wireless data signal by the transmitter. A receiver coil [antenna] is connected to a portion of the vehicle, such as a wheel well member, preferably within three tenths of a meter of the transducer/transmitter coil. Another coil connected to the vehicle may be tuned to receive wheel speed signals from the xe2x80x9cknown typexe2x80x9d of wheel speed sensor, and these signals are conditioned by the receiver and passed to the controller along with the pressure and temperature signal. The pressure/temperature signal and the wheel speed signal may be distinguished by various known means such as by frequency or modulation design, or a separate receiver can be utilized.
Some of the prior art mounts the tire monitoring and transmitting electronics package on the wheel hub and coaxial to the axis of rotation, often in combination with a device for using the wheel rotation to generate power and/or count revolutions. Examples of this construction are found in U.S. Pat. Nos. 4,229,728; 4,300,120; and 5,315,866 which are described as follows.
U.S. Pat. Nos. 4,229,728 and 4,300,120, incorporated in their entirety by reference herein, both disclose a tire pressure monitor having a self-contained generator-transmitter unit affixed to each wheel comprising a pendulum magnet, and a rotating inductor attached to a circuit board (48) containing the discrete electrical components of the wheel mounted unit. It can be seen that the circuit board is affixed to the wheel around a pin (38) at the center of the wheel""s axis of rotation. The transmitter on the circuit board has an antenna (22), but no details are provided about the antenna""s placement or construction.
U.S. Pat. No. 5,315,866, incorporated in its entirety by reference herein, discloses an indicating device, especially for indicating the state of pressure of a tire, of the type that can be fixed to a wheel in an exactly coaxial position. The device is contained in an openable cylindrical box (6) provided with holes in external box extensions for fixing it to the wheel. The device contained in the box (6) includes: a pressure measuring device (7) is connected by a tube (4) to the tire inflation valve; a transducer/transmitter (8) of which only the printed circuit [board] is shown (seen in FIG. 3 as parallel to the box and wheel, coaxial to the axis of rotation); a rotor (12) attached to the box; and a stator (13) prevented from rotating by a counterweight (14) and a weight (15). The circuit board (8) is shown as coaxial around the central rotor and stator, but the counterweight and weight extend radially out over most of the board (8). No details are given concerning the circuitry of the transducer/transmitter or pressure measuring device, and a transmitting antenna is not mentioned at all.
In addition to sensing, if not measuring/monitoring, pneumatic tire pressure, a variety of systems have been developed to regulate, adjust and/or replenish the pneumatic medium (air) in a tire.
U.S. Pat. No. 5,505,080, incorporated in its entirety by reference herein, discloses a tire pressure management system including a tire condition monitor connected to the tire so as to be interactive with air pressure in the tire for selectively measuring a pressure in the tire, a controller, and a display. The tire condition monitor includes a transmitter and a receiver. The controller also has a transmitter and a receiver connected thereto, and the condition monitor and controller communicate via radio signals. An air compressor is mounted to a wheel of the tire so as to deliver air to an interior of the tire when the pressure of the tire is below a predetermined value. A power generator is connected to the wheel of the tire and includes an alternator magnet assembly and an induction coil assembly which are connected to the wheel of the tire such that relative rotation occurs therebetween as the tire rotates. FIG. 7 illustrates a tire pressure sensor, a temperature sensor, and a pick-up coil for revolution counting, all connected to the microprocessor chip of the condition monitor. The revolution counter is said to be usable xe2x80x9cin place of [a] hubometer.xe2x80x9d
U.S. Pat. No. 5,667,606, (referred to hereinbelow as the xe2x80x9cRenier/Cycloid ""606 Patentxe2x80x9d) incorporated in its entirety by reference herein, discloses a tire pressurizing and regulating apparatus comprising a displacement type air pump axially mounted on a vehicle wheel with an air pressure connection conduit introducing air under pressure generated from the pump into the pneumatic tire. A conventional [mechanical] pressure level mechanism is also provided and connected to the pump for establishing and maintaining a desired air pressure in the tire at a predetermined level. A cam and cam follower arrangement is mounted in the housing for the pump, and a pendulum is mounted for free axial rotation relative to the pump housing. The pendulum is connected to one of the cam or cam follower, and the other is secured to the pump housing for rotation therewith to provide a cam actuated driving movement for the pump.
U.S. Pat. No. 4,742,857, incorporated in its entirety by reference herein, discloses a tire pressure sensor and air supply to maintain desired tire pressure. The disclosed system for detecting the air pressure in each wheel (by means of a moveable magnet pressure sensor) and for effecting inflation or deflation in each wheel (by means of a valve connected to the moveable magnet) while the vehicle is operating, includes a controller and a high pressure reservoir mounted on each wheel. A data processor displays the tire pressure to the vehicle operator and allows for manual actuation of the valve for raising or lowering of the tire pressure.
U.S. Pat. No. 5,413,159, incorporated in its entirety by reference herein, discloses a self regulating tire pressure system and method which employs a bistable valve that allows air from a high pressure reservoir (mounted on the wheel) to replenish the pressure within a tire when it has fallen below an actuating pressure, and discontinues its operation only after the tire pressure has increased to a closing pressure that is greater than the actuating pressure. The system is capable of sensing the frequency, number and duration of the valve""s operations as indications of a slow tire leak, a flat, or a low reservoir pressure condition, respectively.
In a variation that does not require an air pressure supply mounted on the tire, Brazilian Patent No. PI 9603529-3A, incorporated in its entirety by reference herein, discloses a system with one or more minicompressors with pressure sensors mounted in the vehicle and coupled to the tires by means of rotating air couplings.
According to an aspect of the invention, a system for monitoring pneumatic tire conditions for one or more tire/wheel assemblies mounted on a vehicle; each tire/wheel assembly comprising a tire mounted on a wheel or wheel carrier; and the system comprising: a transponder with a transmitting antenna mounted on the wheel or wheel carrier of the one or more tire/wheel assemblies for transmitting a signal indicating the condition of the tire of the one or more tire/wheel assemblies, one or more receivers each having one or more receiving antennas fixedly mounted on the vehicle, and circuitry for processing the signals received by the one or more receiving antennas to determine the condition of the tire of the one or more tire/wheel assemblies; the system is characterized in that: circuitry for each transponder is on a printed circuit board within a protective housing coaxial to the hub of the wheel or wheel carrier; and each transmitting antenna is selected from the group comprising a partial loop antenna, a helical antenna, a circular dipole antenna, and a small coupling coil adjacent to an endless hoop antenna.
According to the invention, when the partial loop antenna is selected as the transmitting antenna; the partial loop antenna is affixed on a surface of the printed circuit board around a portion of the circumference of the printed circuit board, and has an angular arc length; and the partial loop antenna comprises a serpentine portion for increasing the effective length of the partial loop antenna without also extending the angular arc length. Optionally, the transponder comprises one or more RF transmission-interfering objects; and the angular arc length and the affixed placement of the partial loop antenna are determined for avoiding interference. Optionally, the partial loop antenna comprises an end portion adjacent to a trimming scale imprinted on the printed circuit board, for indicating locations for trimming the end portion as a guide to proper antenna trimming. Optionally, the partial loop antenna end portion is trimmed to enable tuning of the antenna for optimum transmission at different radio transmission frequencies.
According to the invention, the system comprises a pump system mounted on the wheel or wheel carrier of the one or more tire/wheel assemblies for tire pressure regulation; and a tire pressure sensor connected to the wheel or wheel carrier transponder for measuring the tire pressure.
According to the invention, the transmitted signal comprises a message packet short enough to transmit within less than one revolution period of the wheel or wheel carrier when the vehicle is moving at its fastest expected speed. Preferably, the message packet begins with a 10 bit sync pattern which is not further encoded; and the remainder of the message packet comprises data bits ending with an 8 bit CRC which is encoded, wherein the remainder is encoded by a 4B/5B coding scheme using straight NRZI for bit determination.
According to another aspect of the invention, a system for monitoring automatic tire pressure maintenance for one or more tires of a vehicle, wherein a pump system in a housing attached to each of one or more wheels or wheel carriers of the vehicle is utilized to automatically maintain a setpoint pressure in a pneumatic tire mounted on the wheel or wheel carrier, the system is characterized by: a transponder mounted in the housing with the pump system, wherein circuitry for the transponder is on a printed circuit board within the housing and coaxial to the hub of the wheel or wheel carrier; a transmitting antenna associated with the transponder; a receiver mounted on the vehicle; a receiving antenna associated with the receiver; a tire pressure sensor connected to the transponder; and a control circuit associated with the transponder for measuring the tire pressure using the tire pressure sensor, for converting the tire pressure measurement to an RF signal, and for transmitting the RF signal to the receiving antenna and receiver using the transmitting antenna.
According to the invention, the transmitting antenna is selected from the group comprising a partial loop antenna, a helical antenna, a circular dipole antenna, and a small coupling coil adjacent to an endless hoop antenna. Preferably, the partial loop antenna is selected as the transmitting antenna; the partial loop antenna is affixed on a surface of the printed circuit board around a portion of the circumference of the printed circuit board, and has an angular arc length; and the partial loop antenna comprises a serpentine portion for increasing the effective length of the partial loop antenna without also extending the angular arc length. Furthermore, the system comprises one or more RF transmission-interfering objects contained in the housing; and the angular arc length and the affixed placement of the partial loop antenna are determined for avoiding interference. Optionally, the transmitted signal comprises a message packet short enough to transmit within less than one revolution period of the wheel or wheel carrier when the vehicle is moving at its fastest expected speed. Preferably, the message packet begins with a 10 bit sync pattern which is not further encoded; and the remainder of the message packet comprises data bits ending with an 8 bit CRC which is encoded, wherein the remainder is encoded by a 4B/5B coding scheme using straight NRZI for bit determination.
According to the invention, the pump system comprises a pendulum; the transponder circuitry comprises one or more coils for interacting with the pendulum to determine a revolution angular position or a revolution count; and the control circuit includes the revolution count in the transmitted RF signal.
According to the invention, a temperature sensor is connected to the transponder for measuring temperature; and the control circuit includes the temperature measurement in the transmitted RF signal.
According to the invention, the receiver is a single unit; and a display is associated with the receiver for informing a vehicle operator about tire pressure maintenance for each of the one or more tires. Preferably, the receiving antenna is a single antenna; and the control circuit associated with the transponder on each of the one or more wheels or wheel carriers of the vehicle includes a unique transponder identifying code in the transponder""s RF signal.
According to an aspect of the invention, a pneumatic tire condition monitor in combination with a tire pressurizing and regulating apparatus for one or more tires of a vehicle, wherein the apparatus is in a housing attached to each of one or more wheels or wheel carriers of the vehicle, the monitor is characterized by: a partial loop antenna mounted in each housing with the apparatus, affixed on a printed circuit board which is coaxial to the hub of the wheel or wheel carrier; the partial loop antenna is affixed around a portion of the circumference of the printed circuit board, having an angular arc length; the partial loop antenna comprises a serpentine portion for increasing the effective length of the partial loop antenna without also extending the angular arc length; and the angular arc length and the affixed placement of the partial loop antenna are determined for avoiding RF signal interference due to interaction with signal-interfering objects in the housing. Optionally, the partial loop antenna has an end portion which is trimmed for adjusting the effective length to enable tuning of the antenna for optimum transmission at different radio transmission frequencies.
Other objects, aspects, features and advantages of the invention will become apparent in light of the following description thereof.